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A U-tube contains water and methylated spirit separated by mercury.The mercury columns in the two arms are in level with 10cm of water in one arm & 12.5cm of spirit in the other.What is specific gravity of spirit ?

$\begin{array}{1 1}(A)\;0.7\\(B)\;0.8\\(C)\;1\\(D)\;1.2\end{array} $

1 Answer

Height of the spirit column $h_1=12.5cm=0.125m$
Height of the water column $h_2=10cm=0.1m$
$\rho _0=P_{atm}$
$\rho _1$=Density of spirit
$\rho _2$=Density of water
Now $\rho_B=\rho_D$
$\Rightarrow P_0+h_1\rho_1g=P_0+h_2\rho_2g$
$\Rightarrow \large\frac{\rho_1}{\rho_2}=\frac{h_2}{h_1}$$=0.8$
Put the value & get
Specific gravity of spirit =0.8
Hence (B) is the correct answer.
answered May 9, 2014 by sreemathi.v

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